Damper required in range exhaust hood

Quote:

Originally Posted by Bob Mariani

use an inline damper for this, not the roof cap. The cap should have an insect screen also.

Yup, a damper required by M1502.1: "Range hoods shall discharge to the outdoors through a single-wall duct. The duct serving the hood shall have a smooth interior surface, shall be air tight and shall be equipped with a backdraft damper...."

I would insulate with more than the R-7 required by some codes. The idea is to stop condensation and grease from depositing on the pipe insides. You want the pipe as warm as possible. I would use a roof cap damper w. screen rather than an in-line damper that lets cold air in the rest of the pipe when the unit is not being used. The attic temperature will help temper the pipe a little more, to stop condensation if the pipe was warmer than the outside air. And..... Welcome to the forum!
Be safe, Gary

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17,000 dryer fires a year, when did you last clean the inside of the dryer near motor or the exhaust ducting?